Tin (II) =Triflate

Abstract

Tin (II) =trifluoromethanesulfonate (triflate), easily prepared from tin (II) chloride and trifluoromethanesulfonic acid, is employed for the generation of tin (II) enolates from the corresponding ketones and 3-acylthiazolidine-2-thiones. The tin (II) enolates thus formed react smoothly with aldehydes or ketones to afford the corresponding aldol products in highly stereoselective manner. According to this procedure, various kinds of synthetically useful polyoxygenated compounds are obtained stereoselectfirely.
The most characteristic property of tin (II) enolates is that high asymmetric induction is realized only by the addition of chiral diamines derived from (L) -proline as ligands to the center tin (II) metal. Thus, highly optically active aldols are obtained starting from two different achiral carbonyl compounds. It should be noted that, in some cases, relative stereochemistry of aldols can be controlled by the addition of a diamine as a ligand to the intermediate tin (II) enolates.